There have also been calls for calm after violent reprisals against Sunnis following the attack, raising fears of civil war in Iraq.

Following is a selection of comments:

Ibrahim al-Jaafari, the Iraqi prime minister: "I announce on this occasion three days of mourning. I hope our heroic people will take more care on this occasion to bolster Islamic unity and protect Islamic brotherhood and Iraqi national brotherhood."

Condoleezza Rice, the US secretary of state: "The only people that want a civil war in Iraq are the terrorists like [Abu Musab] al-Zarqawi. Iraqis want to be a stable and unified country. The Iraqi people are working under extremely difficult circumstances to bridge sectarian differences that were always dealt with by repression and violence..."

The UN Security Council: "The members of the Security Council understand the anguish caused by the attacks but urge the people of Iraq to defy its perpetrators by showing restraint and unity."

Mahmoud Ahmadinejad, the Iranian president, who has accused Israel and US forces of being behind the attacks: "These heinous acts are committed by a group of Zionists and occupiers that have failed. They have failed in the face of Islam's logic and justice."

George Bush, the president of the United States: "This senseless crime is an affront to people of faith throughout the world. The United States condemns this cowardly act in the strongest possible terms... Violence will only contribute to what the terrorists sought to achieve by this act... And the American people pledge to work with the people of Iraq to rebuild and restore the Golden Mosque of Samarra to its former glory."

Grand Ayat Allah Ali al-Sistani
rarely speaks publicly

Grand Ayat Allah Ali al-Sistani: "If the security systems are unable to secure necessary protection, the believers are able to do so with the might of God."

Tony Blair, the British prime minister: "The perpetrators of this act had one motive and one alone. They want to cause strife and violence between Sunni and Shia to derail democracy currently taking hold in Iraq. People must not fall into the trap being set for them. It is vital that all groups in Iraq show restraint in the face of this blatant provocation... The British government stands ready to contribute to the reconstruction of the shrine site."

Jalal Talabani, the Iraqi president: "This new ugly crime comes as a warning that there is a conspiracy against the Iraqi people to spark a war among brothers. God willing, we will not allow this... We must cooperate and work together against this danger, the danger of civil war. This is the fiercest danger because it threatens our unity and our country with a devastating civil war."

Ayat Allah Ali Khamenei, the Iranian Supreme Leader: "This is a political crime and its origins should be found in the intelligence organisations of the occupiers of Iraq and the Zionists... There are definitely some plots to force Shiites to attack the mosques and other properties respected by the Sunnis. Any measure to contribute to that direction is helping the enemies of Islam and is forbidden by Sharia."

Zalmay Khalilzad, the US ambassador to Iraq, and General George Casey, in a joint statement, said: "We denounce in the strongest terms the terrorist destruction of the Golden Mosque... This heinous crime is a deliberate attempt to foment sectarian strife in Iraq and the region. Given the historic, cultural and religious importance of this shrine, this attack is a crime against humanity."

Muqtada al-Sadr, Iraqi Shia religious leader: "We ask Iraqis to rise to the responsibility and the scope of this tragedy and maintain the unity and safety of Iraq. My message today to the Iraqi people is to show solidarity and not to fall prey to projects aimed at compromising the unity of the country."

Shaikh Abd al-Salam al-Qubaisi, spokesman for the Association of Muslim Scholars, an influential Sunni Muslim group: "(We) point the finger of blame at certain Shiite religious authorities for calling for demonstrations... I call on Muqtada al-Sadr to interfere because some matters are linked to his group."

Iraqi Islamic Party: "(The party) strongly condemns this sinful act and calls for a wide-reaching and objective investigation to catch those behind this crime that aims to harm the Iraqi people by provoking destructive sectarian strife."

Mowaffaq al-Rubaie, Iraqi national security adviser: "They will fail to draw the Iraqi people into civil war as they have failed in the past."